The median basilic or cephalic vein is chosen by preference. The skin is cleaned as for a hypodermic injection and a bandage is placed about the arm to make tense the veins, as explained under transfusion. The syringe should have a rather short needle with a short bevel at its point. The syringe having been made ready for use, the arm is held with one hand, the fingers and thumb of which should be on either side of the vein chosen and drawing the skin so as to immobilize the vein.
The needle should now be introduced, slowly upwards into the vein. If it is thrust quickly the chances are that it will slip over the vein without penetrating it, while introduced slowly one can usually feel when the wall has been pierced. If, however, there is any doubt, draw back the piston of the syringe a trifle, when, if properly placed, blood will immediately pass into the syringe where it may be seen. If the needle is not in the lumen of the vessel practically no blood will be aspirated, and a few air bubbles will make their appearance Having made certain of the correct placing of the needle, remove the bandage from the arm and inject the contents of the syringe. If any swelling appears during the injection, it is sure evidence that the needle is not in the lumen of the vein. The injection completed, the needle is withdrawn, and the site of puncture wiped with a little alcohol or bichloride. No dressing is required.